A variety of bis(dihydrocarbyl phosphate) compounds are known to persons of ordinary skill in the art who might be interested, for example, in using such organophosphorus compounds as flame retardants for polymers. Examples of bis(hydrocarbyl phosphate) compounds which contain various types of bridging groups between the two phosphate moieties can be found by consulting the following: Japanese Kokai No. 10 74/40,342 (aliphatic divalent groups which can contain an ether bond); U.S. Pat. No. 3,869,526 (aliphatic straight, branched or cyclic organic alkylene residues or a hydrocarbon ether residue); Japanese Kokai No. 82/174,331 (phenyl, bisphenol A-derived, biphenyl, etc.); U.S. Pat. No. 4,343,732 (a residue of a polyhydric alcohol Or phenol or of a polyoxyalkylene glycol).
Japanese Kokai No. 82/55,947 depicts a rather wide variety of bisphosphate compounds with differing bridging groups including those containing multiple phenyl rings in the bridging group but not one containing a nucleus derived from phenolphthalein, also termed "3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone".
Copending applications which describe certain bis(dihydrocarbyl phosphates) include: U.S. Ser. No. 374,716, filed Jul. 3, 1989 and U.S Ser. No. 374 718, filed Jul. 3, 1989.
The use of phenolphthalein-based polymers, as contrasted to monomeric bis(hydrocarbyl phosphates), as flame retardants is disclosed in the following three literature references: J. Polym. Sci., Chem. Ed., Vol. 19, pages 2151, 2659, and 2773 (1981). In addition, the following patent documents indicate the flame retardant characteristics for a variety of phenolphthalein-containing polymers. U.S. Pat. Nos. 4,057,532 (phenolphthalein polyesters); 4,134,936 (copolycarbonates of phenolphthalein polycarbonates and other polycarbonates); and 4,167,536 (organopolysiloxanephenolphthalein-polycarbonate copolymers).
Japanese Kokai No. 74/88,928 describes fire resistant thermoplastic compositions which contain a phosphate, phosphonate, phosphite or phosphinate polyester (a polymeric additive also) of phenolphthalein containing bromine or chlorine substituents on the rings.